Para-xylene, an aromatic hydrocarbon, is an important intermediate which finds wide and varied application in chemical syntheses. Upon oxidation, para-xylene yields terephthalic acid. Polyester fabrics and resins are produced from a polymer of ethylene glycol and terephthalic acid. These polyester materials are used extensively in a number of industries and are used to manufacture such items as, for example, clothing, beverage containers, electronic components, and insulating materials.
The production of para-xylene is practiced commercially in large-scale facilities and is highly competitive. Concerns exist not only about the effective conversion of feedstock through one or more of isomerization, transalkylation and disproportionation to produce para-xylene and effective separation of para-xylene from the resultant mixture of C8 aromatic isomers, but also with the energy costs and capital costs associated with such processes.
In prior art processes, C9 aromatics are separated from the C8 aromatics, i.e., xylene isomers, by fractional distillation. This requires heating of the admixture to vaporize the C8 and lighter aromatics. A large portion of the isomerization stream must be vaporized to accomplish the C9 separation because the stream is generally composed primarily of C8 and lighter aromatics. This separation requires a substantial amount of energy and associated cost. After the C9 aromatic removal, the C8-containing stream is then recycled into the adsorptive separation unit.
Accordingly, it would be an advance in the state of the art to provide a process for the production of para-xylene, including separation and isomeric formation from an admixture of C8 aromatic isomers, that removes the need to vaporize the isomerized stream for removal of C9 aromatics, thereby lowering operational expenses, in the form of energy consumption, and capital expenditures, in the form of required processing equipment and the size of such processing equipment. It would be a further advance in the state of the art to share a fractionation column between the aromatic conversion process and the xylene separation process, thereby reducing capital costs.